Anti-CRISPR polynucleotides and polypeptides and methods of use

Abstract

Methods and compositions are provided for the use of anti-CRISPR (ACR) proteins in plants, including modulation of Cas endonuclease activity, improvement of frequency of homologous recombination, control of Cas endonuclease activity during various cell cycles, spatial and/or temporal regulation of Cas endonuclease activity in plants, usage in gene activation or repression, as well as reduction of off-target polynucleotide cleavage.

We claim: 
     
       1. A method for modulating the activity of a Cas endonuclease with a target polynucleotide in a cell, comprising providing an anti-CRISPR (ACR) polypeptide having an amino acid sequence at least 90% identical to SEQ ID NO:8 to the cell, wherein the ACR polypeptide decreases the activity of the Cas endonuclease in the cell compared to a control cell comprising the Cas endonuclease but not comprising the ACR polypeptide. 
     
     
       2. The method of  claim 1 , wherein the Cas endonuclease activity is selected from the group consisting of target polynucleotide binding, target polynucleotide nicking, target polynucleotide double-strand-break creation, and target polynucleotide modification. 
     
     
       3. The method of  claim 2 , wherein said target polynucleotide modification is selected from the group consisting of insertion of at least one nucleotide, deletion of at least one nucleotide, substitution of at least one nucleotide, and chemical alteration of at least one nucleotide. 
     
     
       4. The method of  claim 1 , wherein the cell is selected from the group consisting of a plant cell, an animal cell, a mammalian cell, a microbial cell and a fungal cell.